Alternating-current electromagnet



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ROMGNET ALTERNATING CURRENT ELECT 16d OC.

20, 1927 2 SheetsSheet lhumslllllllnmwf INVENTOR //JK Andersen ATTRNEY April 3.0, 1929- N. K. ANDERSEN 1,710,761-

' LTERNATING CURRENT ELECTROMAGNET Filed Oct. 20, 1927 2 Sheets-Sheet 2 FIM. L Figi. Figa l 7/ O I O Niels K. Andersen ATioRNEY Patented Api. 3o, 1929.v

'UNITED STATES PATENT OFFICE.

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ALTEBNATINe-GURRENT mineraoiEAeNri'rK Application filed October 20, 1927. Serial No. 227,401.

. This invention relates .to electromagnets and particularly to electromagnets ofthe alternating-current type.

An object of the invention is to `provide an j alternating-current electromagnet in which the magnetic attraction between the armature and vthe stator shall not fall below a prede* terniined value.

A' further object ofthe invention is to provide an alternating-current electromagnet that shall be adapted for energization from alternating-current circuits independently of -tlie frequency. still further object of the invention is to provide an alternating-current electromagnet that shall be simple in construction and easily manufactured and in which there shall be substantially no vibration between the armature and the stator. l For a fuller understanding of the inven- 'tion, reference may be had to the following description, taken in conjunction with the aocompanying drawing, in which 'z Figure l is a front view, in elevation, of an alternating-current electromagnet einbodying the invention. 1 f Fig. 2 is a view, inside elevation, of the saine device.

Fig. 3 is a view, in section, taken on line 'gfllIl-lll of Fig. 1.

Fig. 4 is a view, 1n side elevation, of a sheetmetal punching or vlamination embodied in the armature of the electromagnet shown in Figs. 1 and .2. Fig. 5 is a view,'in side elevation, of a sheetmetal punching or .lamination embodied in the stator or the core of the `electromagnet of the device shown in 1 and 2.

Fig. 6 is an edge view'1 illustrating the thick- 41) ness of the laminations shown in Figs. 4 and 5, and

Fig. is a series of curves illustrating the variation in magnetic attraction between the armature and the stator or the core of the electroniagnet sliownin Figs. 1 and 2.

. In Figs. land 2 of the drawings, a base l' of cast-metal or other suitable material is illustrated, and a core 2 of substantially E- shape is secured to it. The core comprises a plurality of relatively thin laminatioiis 3 of #magnetic material of substantially E-shape (see Fig. 5).

nations 3 are clamped between angle irons 4 and 5 by meanof bolts 6. Each of the legs The bottom edges oi' the lamiof the laminations 3 are clamped together by bolts which extend through openingsr provided therein. 1

The outer legs of the laininations 3 are provided with aliiied notches 7 which form a rectangular slot in the end 0i' each legoiI the core :tor receiving a conductor 8. In this construction, the conductor 8 is insulated from the core by tubular members 9 of insulating material. On one side of the core, the conductor 8 is bent downwardly against the base 1 and is secured thereto by clips l0.

.The ends of the conductor 8 are provided With terminal clips 11. In order to secure the ends of the conductor 8 to the base 1, stud bolts 12 areprovided to make threaded engagement with the base. As shown, the stud bolts are provided with lock nuts 13 for locking them in place. through tubular insulating members 14 mounted in openings in the terminal clips 1l (see Fig. 3 The clips 11 are insulated from y the base l y insulatingwashers 15.

In order to provide a closed circuit, the endsof the conductor 8 may be connected by a resistor 16, having a'resistance of a predetermined value. 'Ihe resistor may be secured, at its cnds, in intimate Contact with the terminal clips by means of nuts and lock washers 17 the latter being of insulating material and disposed between the resistor and the lock Washers for insulating the conductor from the base.. Tlie'conductor 8 and the'resistor member 16, being .connected together, may be utilized as a shadino coil, for a purpose to be 90 D hereinafter set forth.

In order that'lines of alternating magnetic force may be caused to permeate the legs of the E-shaped core 2, an electromagnet coil 18 is provided to encircle the middle 'leg of the core 2. The coil is provided with a clamping plate 19 and bolts 2O vfor securing it to the.

ase l.

Since the coil 18 is disposed on the middlel leg of the core 2, magnetic flux is caused to flow through the outer legsof the core in the same direction and to return through the middle leg in response to electric current Howing through the coil. If thecoil 18 is energized from a source of alternating power,acur

rent will be induced in the shading coil. The current flowing in the shading coil will produce a magnetic liux in the core. that lags substantially degrees behind the flux produced by the coil 18. The purpose of establishing two magnetic fluxes in the core, that are displaced in phase from each other, will be hereinafter set forth in detail.

The core 2 is provided with an armature 21 of substantially E-shape that comprises a plurality of laminations 22 (see Fig. 4) secured together by bolts or other suitable means. The armature is pivotally mounted at 23 on a supporting arm 24, which, in turn, is pivotally secured at 25 to a bracket 26, the bracket 26'bein secured to the base l. v

The middle Iegs of the laminations constituting the armature 21 and the core 2 are vcut on a bias and of such lengththat an yair gap 27 is provided therebetween when the outer legs ofthe core and the armature are in engagement (see Fig. 2). If an air gap be provided, as shown, the tendency of the armature tostick to the core 2 when the coil 18 is deenergized is obviated.

When the coill 18 is energized, a current is induced in the shading coil comprising the conductor 8 and the resistor 16; Thus,two

Vmagnetic fluxes are developed in the core and the larmature, one by the coil 18 and the other by the shading coil.

.The magnetic attraction or pull resulting between the core and the armature, caused by the lines of magnetic force produced by the coil 18, may be represented by a curve 29 of Fig.'7. This curve illustrates that the pull or magnetic attraction varies between a maximum value and zero.

The magnetic attraction or pull between the armature and the core, resulting from the lines of magnetic force developed b current flowing in the shading coil, may e represented by the curve 30, which indicates also that the magnetic pull varies between a maxi- -mum value and zero.

Since the current induced in the shading coil lags behind the current flowing in the coil 18, the fluxes produced by the respective coils will be displaced in phase by substantially 90 electrical degrees. Since the fluxes acting upon the armature combine to produce a resultant flux, the magnetic attraction or ull between the armature and the core may lie represented by a curve 31 which is a summation of the curves 29 and 30.' Therefore, it will be seen that the minimum magnetic attraction between the armature and the core never falls to zero and, therefore, the armature is held firmly against the core 2. Under such operatin conditions, vibration and chattering of t e armature are substantially eliminated.

the resistance of the shading coil circuit coni trolled by replacing the resistor 16 with another of the proper resistance, the coil 18 of the electromagnet may be utilized on substantially any velectrical circuits of commercial frequency, because the resultant curve 31 may be controlled by governing the amplitude of the curve 30 which, as hereinbefore stated, is determined by the currents flowing in the coil 18 and the shading coil.

The electromagnet, illustrated in the drawings, may be assembled as a compact unitary structure and mounted on circuit breaker panels, or wherever needed, for actuating circuit interrupters or other devices. vSince the magnet is applicable to circuits of `substantially all commercial frequencies, it may be described as a universal electromagnet.

Since various modifications in the device embodying the invention may be made without departing from the spirit and scope thereof, I desire that only such limitations shall be placed thereon as are imposed by the prior art and the appended claims.

I claim asl my invention:

1. In an electromagnet, in combination, a plural-leg magnet core of substantially E- shape, an induction coil disposed on the middle leg for causing lines of magnetic force to permeate the legs of said core, a shading coil wound upon the outer legs and inductively coupled to said induction coil, a resistor for short-circuiting said shading coil to cause lines'of magnetic` force to permeate said core responsive tocurren't flowmg in said induction coil, and means for insulating said resistor and shading coil from the core.

2. In an electromagnet, in combination, a magnet core, .an induction coil for causing lines of magnetic force to flow in a plurality of paths in the core, an larmature for said core, a shading coil inductively coupled with, and responsive to, current flowing in the main coil for causing lines of magnetic force, displaced in phase from the lines induced by the induction coil, to flow in said core, and a removable resistor for short-circuiting said shadin coil, whereby the magnetic pull between t e armature and the core may be reve'ited from falling below a predetermined value while the main coil is energized.

3. In an electromagnet, in combination, a magnet core, a main coil for causing lines of magnetic force to flow in a plurality of paths in the core, an armature for said core, a shading coil inductively coupled with, and responsive to, current flowing in the mainvcoil for causing lines of magnetic force to flow in said core that are displaced in phase from the lines of magnetic force produced by the induction coil, and a removable resistor for short-circuiting said shading coil, whereby the magnetic pull between the armature and the core may be prevented from falling below a predetermined value while' the main coil is energized, said core, coils and armature being assembled as a unitary structure.

4e In an electromagneathe combination with a base, a core of substantiallyE-shape, a coil disposed on the middle leg of the core for causing lines of 'magnetic force to permeate the core, of means for producing a second magnetic flux out of phase with the first magnetic flux comprising a conducto;` looped around said coil and disposed in the outer legs of said core, means -for securing the ends of said conductor to said base, means for insulating the conductor from the core and the base, and a removable resistor member connected to the ends of the conductor.

5. In an electromagnet, a stator of substantially E-shape, aninduction coil disposed on a middle leg thereof, an armature of substan tially E-shape `for cooperating With said stator, a `conductor disposed upon the outer legs of the stator, means for securing the ends of the conductor to the stator, means for insulating the conductor from the stator, and a removable resistor connected to the ends of the conductor whereby a current is induced in said coil responsive to current flowing inthe induction coil for producing lines of magnetic force displaced in phase relation from the lines of magnetic force caused by the induction coil.

6. In an alternating-current electromagnet,

causing lines of magnetic force to ermeate the stator, of a conductor dis ose on the outer legs of said stator, means or insulating said conduct-or from the core, means for securing the terminals of said conductor to said stator and a removable resistor connected to the terminals of said conductor.

7; In an electromagnet, in combination, a plural-leg magnet core, an induction coil disposed on one leg of said core for causing lines of force to permeate the legs of said-core, a shading coil Wound upon the other legs of said core and inductively coupled to said induction coil to cause lines of magnetic force to permeate said core responsive to current owing in said induction coil, and means for varying the resistance of said shading coil.

In testimony whereof, I have hereunto slibscrirlzaed my name this 7 th day of October, 192

NiELs K. ANDERSEN. 

